"home made" parts don't have any place in airplanes. If the carb is leaking the solution is not to turn the fuel off it is to fix the carb !Further investigation showed that the factory swivel connection at the fuel valve had been replaced by a homemade part sometime in the aircraft's history. The valve had become stiff, as they do with age, and this bogus fitting had bent. The bending, combined with the stiffness, resulted in the valve not shutting off completely. This allowed enough fuel for a run-up and taxiing, but not enough to sustain takeoff power. Had the valve shut off properly, the engine would have started but run out of fuel before I got to the run-up bay, thus alerting even me that something wasn't quite right.
Two previous owners had never used the fuel shut-off, and of course had never had a problem, as the valve was always full on. The current owner was in the habit of shutting off the fuel. He had previously owned a Champ and shut the fuel off after each flight due to a leak through the carburettor. I have never shut off the fuel in my Stinson and never even thought about the valve. However, had I taken the time to use the printed checklist stashed up high on the right side of the cabin, none of this would have happened.
For the first time ever the category "mechanical failure" is now the 2nd highest cause of fatal accidents in Canada. This is a worrying trend and completely within the power of the pilot to influence